This project aims to understand mechanisms of visual-motor integration in human frontal and parietal lobes. Interactions among brain systems controlling eye and limb position contribute to visual-motor integration. Gaze influences sensory and motor processing at many brain sites in non-human primates;significantly less is known about how gaze regulates human sensory-motor processing. Determining how gaze and limb motor control interact in parietal and frontal areas seems essential to understand purposeful visual-motor integration. We will use functional MRI and electroencephalography to measure frontal and parietal processing underlying gaze and hand movement interactions. We have recently discovered the existence of gaze gain fields in human parietal and frontal areas;the project will use changes in gain fields and gaze-induced modulation of hand movement brain responses to understand integration of visual input, gaze position and hand movements to arrive at a model of parietal-frontal organization for voluntary action. The project has three aims: First, what are the principles for developing and maintaining gaze gain fields in human parietal and frontal lobes? We will investigate organization and changes in gain fields and gaze-induced modulation of hand movement representations as information passes from parietal to frontal lobe in the vision to action stream. Second, is spatial compatibility between gaze and hand movements required when combining visual input and hand movements as information flows from human parietal to frontal areas? For this aim, we will investigate whether eye-hand spatial compatibility and choice of arm effector have key roles in developing gain fields. Third, what coordinate system do arm movement related areas in parietal and frontal cortex use? In these experiments, we will test whether parietal and frontal areas use eye-, head-, body- or world-centered coordinate frameworks when integrating eye position with arm movements. Collectively, the experiments will determine whether spatial compatibility among location of gaze and arm positions represents a key regulatory feature needed to construct activation and functional connectivity patterns of frontal and parietal areas that mediate eye and hand movements. The results will have application to models of sensory motor integration and how dynamic brain representations become created and modified, especially regarding whether motor plans are formed in the parietal lobe and then relayed to frontal cortex or alternatively that the parietal lobe relays fundamental information to frontal structures for eventual planning.